1. Field of the Invention
The invention relates to an improved fuel injection system for internal combustion engines.
2. Description of the Prior Art
A fuel injection system for internal combustion engines of the type with which this invention is concerned is known from European Patent Disclosure EP 1 176 306 A2, in which, for triggering a fuel injection valve, a servo control circuit is provided, having a control valve which has a control piston which is longitudinally displaceable in a bore and which being triggered by an electromagnetic valve as a switching valve realizes the pressure control of the fuel injection valve. The control valve has a first valve seat, which defines a first pressure chamber, and a second valve seat, embodied as a slide seal, which defines a second pressure chamber. The fuel injection system is embodied without a pressure booster interposed between the pressure reservoir and the fuel injection valve.
From German Patent Disclosure DE 101 23 913 A1, a fuel injection system for internal combustion engines with a pressure boosting device for pressure boosting is known in which a 3-way valve is used to control the injector. Such 3-way valves, embodied as servo valves, as a rule have both an electromagnetically or piezoelectrically triggered switching valve and a control valve with a control piston, which is triggered by the switching valve. Control valves of this kind, which are constructed in a seat-slide embodiment, must control a large return quantity of the pressure boosting device. Various pressure chambers for connection to control lines are necessary on the control piston of the control valve here and are subjected from the inside to system pressure (rail pressure, or the pressure to be switched). This pressure burden causes the leakage gaps in high-pressure-tight guides to widen and causes deformation and widening of the control edges of slide seats and high notch tensions at bore intersections. These effects occurring because of the pressure burden impair the function and hence the durability of the servo valve.